Abstract: ZnO and ZnO∶Co microcrystal were prepared by gas phase reaction.The electron trap energy level structure (donor level) and the photoelectrons temporal process of materials was investigated by thermo-luminescence microwave and absorption dielectric spectrometry respetively. Two peaks was observed in thermo-luminescence spectra of pure ZnO, one is -183 ℃ and the other is -127 ℃, which shows that two kinds of electron trap energy level produced by the intrinsic defects in ZnO. The thermo-luminescence intensity of ZnO∶Co was only 10; of pure ZnO, which shows that the consistency of electron trap is very less. The microwave absorption dielectric spectrometry shows the temporal process of photoelectrons in conduction band in pure ZnO decayed according to exponential, the lifetime of phase photoelectrons is 802 ns. The reason of long lifetime is relaxation effects of electron trap to conduction band photoelectrons. The microwave absorption dielectric spectrometry relative intensity of ZnO∶Co less than one-fifth of the pure crystal ZnO, that shows the density of electron trap is less in ZnO∶Co minicrystal, so photoelectrons are disappeared quickly, and the decay process of photoelectrons is only 10-20 ns. The results show that Co doped ZnO have obvious effect on restrain the formation of electron trap energy level.